The present invention relates generally to a magnetoresistive head for use in a magnetoresistive read device. In particular, the present invention is a magnetoresistive reader and method of fabricating a magnetoresistive reader which thermally isolates a magnetoresistive element from thermal asperities caused by imperfections in a magnetic medium or disc.
A magnetoresistive head consists of two portions, a writer portion and a reader portion, positioned adjacent each other. The inductive writer portion writes magnetically encoded information to a magnetic medium or disc.
A magnetoresistive reader portion of a magnetic head retrieves magnetically-encoded information that is stored on a magnetic medium or disc. The magnetoresistive reader is typically formed of several layers that include a top shield, a bottom shield, a read element, a bias layer, and a spacer layer. The read element, bias layer, and spacer layer are positioned between a top and bottom shields. The read element is fabricated from a magnetoresistive composition, typically a ferromagnetic material such as nickel-iron (NiFe). The bias layer properly biases the read element along an easy axis of lower coeractivity and the spacer layer provides the necessary separation between the read element and the bias layer.
The read element is fabricated on the read head such that the easy axis is transverse to the direction of disc rotation and parallel to the plane of the disc. Magnetic flux from the disc""s surface causes rotation of the magnetization vector of the read element, which in turn causes a change in electrical resistivity of the read element. The change in resistivity of the read element can be detected by passing a sense current through the read element and measuring a voltage across the read element. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
Due to the low-flying nature of a read head, i.e. the read head is positioned within picometers or femtometers to a rotating disc in state-of-the-art technologies, the magnetoresistive reader is susceptible to disc projections or mechanical asperities, which interfere with the read process. Asperities on the disc can come into direct contact with a magnetoresistive read element. When a magnetoresistive read element contacts a mechanical asperity on a disc, the read element undergoes frictional heating and the resistance of the magnetoresistive sensor changes accordingly. This event has been termed a xe2x80x9cthermal asperityxe2x80x9d. A signal spike, having a duration of 1-3 microseconds, will result. During this period, the read element is unable to properly read information from the rotating disc.
Another situation which may inhibit or alter the magnetoresistive reader from properly reading the information stored on a disc stems from the disc having a warped surface, rather than a perfectly planar surface. The magnetoresistive read element is biased causing it to be hot relative to its surroundings. The sensor flies very close to the disc which acts as a large heat sink. The proximity of the read element to the disc changes the rate of cooling of the read element and thereby changes the resistive properties of the read element. Dynamic changes in flying height due to a warped surface, disc and head modulation, and near contact with asperities can all lead to baseline shifts in the resistance of the read element, thereby inhibiting its reading capabilities.
There is a need for a magnetoresistive read transducer that will not be affected by disc projections or mechanical asperities. Thus, the thermal asperities will not cause corruption of the read process.
The present invention is a reader and a method of fabricating a reader having a thermally isolated magnetoresistive element. The method includes fabricating a magnetoresistive read transistor between a bottom shield and a top shield. The magnetoresistive read element is coated with a thermally isolating material. In one preferred embodiment, the magnetoresistive read element is coated with a zirconia compound, such as zirconium diboride. A zirconia compound exhibits high strength, high fracture toughness, and high resistance to impact and cracking. In one preferred embodiment, the zirconia compound can be applied by a magnetron sputtering process in the pole tip region using a photolithography mask.